1. Field of the Invention
The present invention relates to a zoom lens system which has a zoom ratio of approximately 3 covering a wide-angle range to a telephoto range, and which is used in a digital camera having an imaging device such as a CCD or a CMOS.
2. Description of the Prior Art
In recent years, there has been a further demand for higher quality zoom lens systems in order to cope with higher pixelization of imaging devices, and also there has been a demand for faster lens systems having a smaller F-number in order to cope with pixel-miniaturization. However, in reality, zoom lens systems having an F-number in a range from 2.8 to 3.5 at the short focal length extremity are the most predominant in products in the market.
In a typical small zoom lens system used in a compact camera, if attempts are made to achieve a fast lens system having an F-number of approximately 2 at the short focal length extremity, the correcting of various aberrations, e.g., spherical aberration in particular, etc., becomes difficult.
The number of lens elements can, of course, be increased to the extent that these lens elements can constitute four or more lens groups; and thereby, the various aberrations can be corrected. On the other hand, miniaturization of the lens system is sacrificed.